The human skeleton is composed of 206 individual bones that perform a variety of important functions, including support, movement, protection, storage of minerals, and formation of blood cells. To ensure that the skeleton retains its ability to perform these important functions, and to reduce pain and disfigurement, fractured bones should be repaired promptly and properly. External or internal fixation devices (such as casts, bone plates, or nails, among others) may be used on less severe fractures that are reconstructable, to reinforce fractured bones and keep them aligned during healing. However, more severe fractures (or disease), particularly near the end of a bone, may damage the bone sufficiently to preclude reconstruction by fixation only. In these cases, a bone prosthesis may be installed to replace bone, for example, to provide an artificial joint or a portion thereof.
The elbow joint provides an exemplary site of prosthesis installation. The elbow joint is formed at the intersection of the humerus, radius, and ulna bones. In this joint, the radius plays a dual role by movement about two axes so that the elbow can operate as a hinge joint and the forearm can pronate and supinate. To guide and restrict this movement about two axes, the head of the radius (the radial head) includes (1) a concave axial surface for articulation with the capitellum of the humerus and (2) a convex side surface for articulation with the radial notch of the ulna.
Trauma to the elbow joint often involves damage to the radial head. With such trauma, replacement of the radial head with a corresponding prosthesis may help restore the function of the elbow joint. However, this prosthesis may be difficult to install for proper articulation with the ulna and/or humerus.